CERN Accelerating science

Map of planned, current, and completed reactor antineutrino experiments. Text color indicates experimental status, while arrow color indicates the interaction channel used by the experiment. Only completed experiments taking data after 2010 are included. Further description of these experiments are given in Tables~\ref{tab:ibd_experiments} and~\ref{tab:cevns_experiments}.

Illustrations of reactor \nuebar interaction mechanisms. Adapted from~\cite{doi:10.1126/science.aao4050}

Overview of experimental source-detector baselines (L) and neutrino energies (E) sampled by neutrino experiments worldwide; adapted from Ref~\cite{Arguelles:2022bvt}.

Approximate flavor composition of commonly discussed neutrino sources; adapted from~\cite{Formaggio:2012cpf}. Reactor experiments are notable in their use of lower energy neutrinos, their access to very short baselines, and their extreme electron flavor purity.

Expected flavor composition of the reactor antineutrino flux as a function of distance to a reactor core for neutrinos of 4~MeV energy. Figure taken from Ref.~\cite{Vogel:2015wua}. The light yellow region corresponds to the survival probability of $\bar\nu_e$ that reactor antineutrino experiments can measure by placing their detectors at different baselines.

Left: Schematic of the JUNO detector. An acrylic sphere containing 20 kilotons of liquid scintillator serving as the \nuebar detection target is surrounded by 20-inch and 3-inch PMTs. Right: JUNO IBD spectrum with and without neutrino oscillation effects. For illustration purposes, a detector with perfect energy resolution is assumed. The gray dashed curve shows the oscillated spectrum when only the term in the disappearance probability that is modulated by $\sin^2 2\theta_{12}$ is included, whereas the blue and red curves show it when the full oscillation probability in vacuum is used assuming the normal and inverted mass orderings, respectively. Some features driven by the $\sin^2 2\theta_{12}$, $\sin^2 2\theta_{13}$, $\Delta m^2_{31}$ and $\Delta m^2_{21}$ oscillation parameters are shown pictorially. Figures obtained from Ref.~\cite{junooscdiana}.

Left: Schematic of the JUNO detector. An acrylic sphere containing 20 kilotons of liquid scintillator serving as the \nuebar detection target is surrounded by 20-inch and 3-inch PMTs. Right: JUNO IBD spectrum with and without neutrino oscillation effects. For illustration purposes, a detector with perfect energy resolution is assumed. The gray dashed curve shows the oscillated spectrum when only the term in the disappearance probability that is modulated by $\sin^2 2\theta_{12}$ is included, whereas the blue and red curves show it when the full oscillation probability in vacuum is used assuming the normal and inverted mass orderings, respectively. Some features driven by the $\sin^2 2\theta_{12}$, $\sin^2 2\theta_{13}$, $\Delta m^2_{31}$ and $\Delta m^2_{21}$ oscillation parameters are shown pictorially. Figures obtained from Ref.~\cite{junooscdiana}.

JUNO's relative precision on the oscillation parameters as a function of run time. The markers and vertical lines highlight run times of 100 days, 6 years, and 20 years. The horizontal gray dashed line represents a 1\% relative precision. The green dotted and red dotted lines are indistinguishable from each other since the statistical-only precision is essentially identical for the $\Delta m^2_{31}$ and $\Delta m^2_{21}$ parameters. Figure obtained from Ref.~\cite{junooscdiana}.

Left: Current constraints on a sterile neutrino from $\nu_e$/$\overline{\nu}_e$ disappearance. Color fillings represent preferences; hatching represents exclusions. The dashed, gray region is the fit to reactor rate deficits using the HM flux model \cite{Giunti:2021kab}, given for context. See text for more details. Right: The future sensitivities of KATRIN \cite{KATRIN:2022ith} (green; 95\% C.L.), PROSPECT-II \cite{Andriamirado:2021qjc} (purple; 90\% C.L.), DANSS (light blue; 90\% CL$_s$) and JUNO-TAO \cite{juno_tao} (cyan; 90\% CL$_s$). For PROSPECT-II, two configurations are shown: two years at an HEU core (solid), and four years at an HEU core plus two years at an LEU core (dashed). The dot-dashed gray line is the $CP$ violation disambiguation limit relevant for DUNE \cite{KayserVal}.

Left: Current constraints on a sterile neutrino from $\nu_e$/$\overline{\nu}_e$ disappearance. Color fillings represent preferences; hatching represents exclusions. The dashed, gray region is the fit to reactor rate deficits using the HM flux model \cite{Giunti:2021kab}, given for context. See text for more details. Right: The future sensitivities of KATRIN \cite{KATRIN:2022ith} (green; 95\% C.L.), PROSPECT-II \cite{Andriamirado:2021qjc} (purple; 90\% C.L.), DANSS (light blue; 90\% CL$_s$) and JUNO-TAO \cite{juno_tao} (cyan; 90\% CL$_s$). For PROSPECT-II, two configurations are shown: two years at an HEU core (solid), and four years at an HEU core plus two years at an LEU core (dashed). The dot-dashed gray line is the $CP$ violation disambiguation limit relevant for DUNE \cite{KayserVal}.

Current bounds and projected sensitivity bounds for new neutrino interactions with nucleons through a scalar mediator (left) and vector mediator (right). Plots show with different colors the parameter space ruled out using neutrinos from accelerator complex and neutrinos from nuclear reactor facilities. Figures taken from \cite{fernandezmoroni2021physics}.

\textbf{Left:} The expected reactor CEvNS energy spectra in a Si/Ar/Ge/Xe target, with the assumption of 1kg target mass and 25m standoff distance from a 1GW reactor core; reactor antineutrino spectrum is taken from \cite{vogel_review}. \textbf{Right:} Integrated CEvNS event rate in 1 kg of Si/Ar/Ge/Xe as a threshold of detector energy threshold, with the same assumption on reactor parameters as for the left figure.

\textbf{Left:} The expected reactor CEvNS energy spectra in a Si/Ar/Ge/Xe target, with the assumption of 1kg target mass and 25m standoff distance from a 1GW reactor core; reactor antineutrino spectrum is taken from \cite{vogel_review}. \textbf{Right:} Integrated CEvNS event rate in 1 kg of Si/Ar/Ge/Xe as a threshold of detector energy threshold, with the same assumption on reactor parameters as for the left figure.

Comparison of sensitivity of axion like particles searches at nuclear reactor compared with excising bounds. Figures taken from \cite{Dent_2020}.

Allowed regions for isotopic IBD yields of \uFive, \pNine, and \uEight~provided by a fit of time-integrated and `flux evolution' IBD yield datasets. For this fit, sterile neutrino oscillations are assumed to be negligible. From Ref~\cite{giunti_diagnose}.

The 95\% C.L. (dark) and 99\% C.L. (light) contours in $r_{235}$--$r_{239}$ plane for integrated rate (red), fuel evolution (purple) and all reactor experiments (black), where $r_{X}$ is the ratio of the flux predicted/measured for isotope $X$ over its HM prediction. The result from STEREO \cite{stereo_rate} is shown in green; the bands represent the $1\sigma$ (dark) and $2\sigma$ (light) regions for one degree of freedom. The orange, blue and cyan ellipses represent the expectations from the HM, EF and HKSS flux models, respectively; $1\sigma$ ($2\sigma$) is shown in dark (light) shades. The brown bands represent the $1\sigma$ (dark) and $2\sigma$ (light) determination of the $^{239}$Pu/$^{235}$U ratio from the Kurchatov Institute \cite{Kopeikin:2021rnb, kopeikin2021}. The black, dashed line represents the line along which $r_{235}=r_{239}$. The triangles represent the best-fit values for the three fits, and the circles show the central values for the flux models. Figure and caption adapted from Ref.~\cite{huber_berryman}.

Joint unfolded interacting antineutrino energy spectrum of $^{235}$U and $^{239}$Pu from Daya Bay and PROSPECT (left) and of $^{235}$U from STEREO and PROSPECT (right). Comparisons to the Huber-Mueller model are given in both cases. From~\cite{bib:prosDBjoint} and~\cite{bib:prosSTEREOjoint}.

Left: PROSPECT-II $^{235}$U spectrum measurement uncertainties after two years of data-taking. From~\cite{Andriamirado:2021qjc}. Right: Comparison of projected JUNO-TAO and JUNO measurements and uncertainties with Daya Bay measurements, assuming that the true LEU reactor spectrum measured by JUNO-TAO and JUNO is given by Ref.~\cite{bib:fallot2}; JUNO-TAO's sensitivity to fine structure in the LEU reactor antineutrino spectrum is clearly illustrated. From Ref.~\cite{juno_tao}.

Left: PROSPECT-II $^{235}$U spectrum measurement uncertainties after two years of data-taking. From~\cite{Andriamirado:2021qjc}. Right: Comparison of projected JUNO-TAO and JUNO measurements and uncertainties with Daya Bay measurements, assuming that the true LEU reactor spectrum measured by JUNO-TAO and JUNO is given by Ref.~\cite{bib:fallot2}; JUNO-TAO's sensitivity to fine structure in the LEU reactor antineutrino spectrum is clearly illustrated. From Ref.~\cite{juno_tao}.